It is known to package products together in packs. These packs are often shrink-wrapped. The shrink wrapping process involves passing the pack, which has been draped with shrink film, through a shrink tunnel.
Within the shrink tunnel are arrays of nozzles that blow hot air against the shrink film. To promote good shrink wrapping, it is useful for these nozzles to be pointed to target specific regions of the package. To assist in targeting the correct places on a package, it is useful to provide shutters over some nozzles.
It is often desirable to direct hot air leaving the nozzles so that it strikes the packs just below the top of the containers first. It is also often desirable to protect certain parts of the pack from hot air. These can both be achieved by covering selected nozzles with at least one shutter or guide plates.